1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method implemented in a printer that prints after tone-corrected data is spooled thereto, and whereby automatic tone correction is conducted during the print job.
2. Description of the Related Art
In recent years, most color printer models are equipped with automatic tone correction in order to provide consistent color reproduction. At the same time, the number of cases wherein consistent image quality is demanded even in monochrome binary printers is increasing, thus requiring automatic tone correction in order to provide consistent tone.
In addition, the number of printed pages in an office is not significantly large, and thus if automatic tone correction is conducted during a print job, the user is made to wait for printing. For this reason, it has been typical to not conduct automatic tone correction during print jobs. However, in POD (Print on Demand) environments wherein a printer is used like a printing press, the number of printed pages is extremely large, and the printer is used differently than in an office. In addition, since POD involves commercial printing wherein printed material is sold, the demands made with respect to image quality are becoming stricter. Given the above, there is a need to improve image quality consistency in POD environments by conducting automatic tone correction even during print jobs.
In automatic tone correction, it is necessary to conduct tone correction for all screens being used. The screen ruling for each halftone screen differs, and the binarized pattern dither matrix like that shown in FIG. 23 differs for each screen. Even if the same multi-valued data is binarized according to the dither matrix, the patterns and shapes colored black will differ, thereby causing the output tones to differ. For this reason, it is necessary to create tone correction lookup table for each screen.
In the case of output by means of copying, for example, error diffusion screens and tone screens for copying may be used as the screens. In the case of output by means of developing a PDL (Page Description Language) to output with high quality, PDL high-resolution screens, PDL low-resolution screens, or PDL tone screens become necessary. And in case of output by means of copying and the PDL with more than one resolutions, screen is necessary for each resolution.
Japanese Patent Laid-Open No. 2003-270868 discloses technology related to screens used in automatic tone correction, wherein information regarding a screen used in screening set in a print control unit is received. Subsequently, tone correction is conducted using a tone correction patch whereby an image was formed with the screen used in the screening, thereby making it possible to improve tone correction precision.
Japanese Patent Laid-Open No. 2005-111714 discloses technology related to saving and deleting bitmap data, wherein saved bitmap data is deleted when the number of times the bitmap data is used is low, thereby making effective use of storage space.
However, in automatic tone correction, it is necessary to create tone correction lookup table for all of a large number of screens used, and thus automatic tone correction processing has been time-consuming.